This invention relates to a vibration isolating device for damping vibrations from vibration source.
The vibration isolating device generally known as a rubber vibration isolator is used, for instance, as an engine mount for automobile vehicles, whereby vibrations from an internal-combustion engine are absorbed so as not to be transmitted to a vehicle chassis.
A proposed vibration isolating device of this type comprises two vibration-damping fluid chambers separated by an orifice-formed partition, in which vibrations from vibration source are absorbed by a flow resistance subjected to the fluid when the vibration is transmitted to the one chamber. This allows flow of the fluid from the one chamber to the other through the orifice.
Such a conventional vibration isolating device is effective for damping the vibrations of low frequency, but is not effective against vibrations to be input having a high frequency of, for example, about 50 Hz or more. In the latter case, since the amplitude of the vibration is small, the orifice is in a clogged state, so that the internal pressure of the fluid chamber rises and also the spring constant increases. As a result, the vibration transmissibility inversely increases to deteriorate the ride feeling on the vehicle.